Leases - Reconciliation of Undiscounted Future Minimum Lease Payments Remaining Under Leases that Have Not Yet Commenced and Other Operating Leases (Detail) $ in Thousands	Sep. 30, 2019 USD ($)
Undiscounted future minimum lease payments:
2019 (remainder of year)	$ 594
2020	3,470
2021	4,968
2022	6,051
2023	6,848
Thereafter	83,731
Total undiscounted future minimum lease payments	105,662
Current portion of operating lease liabilities	(2,506)
Operating lease liabilities, non-current	4,320
Leases Not Yet Commenced [Member]
Undiscounted future minimum lease payments:
2019 (remainder of year)	73
2020	413
2021	2,306
2022	5,420
2023	6,369
Thereafter	83,731
Total undiscounted future minimum lease payments	98,312
Other Operating leases [Member]
Undiscounted future minimum lease payments:
2019 (remainder of year)	521
2020	3,057
2021	2,662
2022	631
2023	479
Total undiscounted future minimum lease payments	7,350
Amount representing imputed interest	(524)
Total operating lease liabilities	6,826
Current portion of operating lease liabilities	(2,506)
Operating lease liabilities, non-current	$ 4,320